In the early days of germ theory, contagious diseases were thought to be caused by fungi or bacteria. In the 1890s, Dmitri Ivano
vski filtered extracts from diseased tobacco plants and discovered that the disease could be transmitted to new plants through the filtrate. He concluded that the disease was caused by particles smaller than bacteria: the tobacco mosaic virus.
"In the early days of germ theory, contagious diseases
were thought to be caused by fungi or bacteria. In the 1890's, Dmitri
Ivanovski filtered extracts from diseased tobacco plants and discovered
that the disease could be transmitted to new plants through the
filtrate. He concluded that the disease was caused by particles smaller
than bacteria; the tobacco mosaic virus", is partially correct. Dmitri
Ivanovski discovered that filtered extracts from diseased tobacco plants
could be transmitted to new plants through the filtrate. However, it
was Dutch microbiologist Martinus Beijerinck who, while replicating
Ivanovsky's experiments, proved that the filtrate contained a new
infectious agent. Beijerinck named this agent a virus.
As a result of meiosis in the male and female sex organs of a plant, male and female gametes or male and female sex cells produced respectively. Gametes are universally haploid. Male and female gametes fuse or fertilize to form a diploid zygote. A zygote or fertilised egg is a one-celled structure which later develops into an embryo.
In a long bone, the epiphyseal is the growing region. In young bones, bone formation occurs in a layer of hyaline cartilage. The epiphyseal plate forms cartilage on the epiphyseal end. Cartilage is calcified on the diaphyseal side, and the diaphysis lengthens.
Six thousand reindeer once lived on a remote island in the Bering Sea
that was briefly their paradise. In what has become a classic story of
wildlife boom and bust, no reindeer live on St. Matthew Island now.
Three scientists just looked back at the St. Matthew's reindeer herd and
found that an extreme winter probably pushed the stressed animals to
their deaths.
